1. Field of the Invention
The present invention relates to a disk cartridge in which a disk medium to be used as a recording/reproducing medium for information processing or the like is rotatably accommodated while preventing any intrusion of dust or the like.
2. Description of the Related Art
There has been conventionally used a disk medium such as an optical disk or a magneto-optical disk as a recording/reproducing medium for a portable computer. In such a disk medium, information is recorded by forming a pit, changing a phase or magnetizing, caused by decomposition of a pigment layer on a recording side by irradiating the recording side with a laser beam while the disk medium is rotated in the state in which it is loaded in a drive device. Moreover, such a disk medium is designed to reproduce the information recorded according to a reflectance ratio or a difference in polarizing angle of a laser beam.
Furthermore, in such a disk medium, there has been conventionally proposed to shorten a wavelength of the laser beam for irradiating the recording side so as to increase a recording capacity. In the case where the information is recorded or reproduced by using the laser beam having a short wavelength (for example, a violet laser beam), it is necessary to reduce the thickness of a cover layer, which protects the recording side of the disk medium, in order to suppress attenuation of the laser. However, if the thickness of the cover layer is reduced, the surface of the cover layer, i.e., an aperture of the laser beam at a surface exposed to the outside becomes smaller, and an influence of dust or the like adhering to the surface of the cover surface cannot be disregarded.
Therefore, there has been used a disk cartridge in which a disk medium is accommodated in a case, to prevent any adhesion of dust or the like to the disk medium. Such a disk cartridge comprises an opening for allowing a part of a center hole (i.e., a center core) formed at the center portion of the disk medium and a part of a recording side (i.e., a cover layer) to be exposed to the outside, and a shutter member for opening/closing the opening.
In the disk cartridge, the opening is normally shut by the shutter member so as to prevent of dust or the like intruding inside the disk cartridge, that is, so as to prevent any adhesion of dust or the like to the disk medium. When the disk cartridge is loaded in the drive device, the opening is opened, and the center hole (i.e., the center core) can be held by a rotary spindle and a laser head can approach to the recording side (namely, can irradiate the recording side with the laser beam).
In the disk cartridge of this type, miniaturization and thinning are desired while it is necessary to secure a space for accommodating the shutter member therein in the state in which the opening is opened. Japanese Patent Application Laid-open (JP-A) No. 2000-30394 discloses a disk cartridge in which miniaturization and thinning are achieved by dividing a shutter member into two parts.
The disk cartridge disclosed in the above-described Application is configured in such a manner as to shut the entire opening in the state in which the end of a first shutter member, which mainly shuts an opening portion for inserting a laser head thereinto (i.e., for allowing a laser head to approach), abuts against the end of a second shutter member, which mainly shuts an opening portion for inserting a rotary spindle thereinto. These first and second shutter members are pivoted in different directions while the mutual abutting ends are separated from each other in the state in which the opening is opened, so that both of the shutter members can be accommodated inside a accommodating space substantially equivalent to projected area of a disk medium. Consequently, it is possible to prevent any adhesion of dust or the like to the disk medium, and further, to reduce the size and thickness of the disk cartridge.
A case for rotatably accommodating the disk medium therein is formed by, for example, joining an upper shell and a lower shell to each other, in which an opening for an access to the disk medium is formed at the lower shell. The shutter member for opening/closing the opening is movably accommodated between a covering-plate having a similar opening formed thereat and the lower shell. Namely, an actuating member for opening or closing the shutter member is disposed on one of side walls of the disk cartridge. When the disk medium is loaded in a drive device, the actuating member abuts against an unlock member disposed in the drive device, and thus, is pressed relatively backward, so that the shutter member is moved (i.e., pivoted), thereby opening the opening.
In the disk cartridge with the above-described configuration, the disk medium is loaded in the drive device, so that the center core portion of the disk medium is held in the rotary spindle in the drive device. Therefore, it is necessary to set the center core with respect to the rotary spindle accurately. Thus, positioning the disk cartridge in the drive device is a very important matter.
In the disk cartridge as disclosed in the above-described Application, for example, reference holes are formed at right and left corners at the lower surface backward in the direction in which the disk cartridge is loaded in the drive device. When positioning members of the drive device are inserted into the reference holes, the disk cartridge can be positioned in the drive device. Conventionally, a sensor member of a contact type is disposed at the lower surface of a disk cartridge inserting port in the drive device, and the front side wall of the disk cartridge is brought into contact with the sensor member, so as to actuate the above-described positioning members. The contact of the front side wall of the disk cartridge in this way is intended to actuate the positioning members initially.
As shown in FIG. 21, in such a manner as to recognize the direction to insert the disk cartridge into the drive device from the external appearance, for example, the disk cartridge of this type may have its front side wall, which is first inserted into the drive device, formed in an arcuate shape in plan view, which is a different shape from other side walls. However, when the front side wall of the disk cartridge is formed into an arcuate shape, a deficiency such as inaccurate contact with a sensor member 206 or 208 (in this case, a sensor member 206) in the drive device when the disk cartridge is inserted into the drive device may easily occur. Therefore, the drive device and the disk cartridge may not be able to be uniquely positioned, thereby arising a problem that the center core cannot be accurately set with respect to the rotary spindle.
Furthermore, the lateral width of the disk cartridge is set slightly smaller than that of the disk cartridge inserting port formed at the drive device in such a manner that the disk cartridge can be smoothly loaded in the drive device. Therefore, the disk cartridge is designed to be loaded in the drive device with a slight space kept with respect to the disk cartridge inserting port. Consequently, the positional accuracy of the disk cartridge with respect to the drive device is liable to become unstable, resulting in difficulty in securing the positional accuracy of the disk cartridge with respect to the rotary spindle or the laser head.
Moreover, in the case when the size of the actuating member for opening/closing the shutter member of the disk cartridge is small, there may be a risk that deficiencies such as the actuating member fails to contact an unlock member in the drive device occur. If the actuating member fails to contact the unlock member, there occurs a trouble that the opening cannot be opened. Additionally, since dimensional errors generated in molding each of a plurality of members (for example, an upper shell, a lower shell, a covering-plate and the like) are compounded up in the disk cartridge configured by assembling the members, it has been conventionally difficult to enhance dimensional accuracy, in particular, in the entire height (thickness) of the disk cartridge.